Electronic conferencing services, such as web conferencing, video conferencing, and web casting, provide essential means by which people can communicate and collaborate. As is known, two or more people may conduct an electronic conference over a computer network, such as the Internet, using conferencing software running on local computing machines. Each participant in an electronic conference operates a computing machine (e.g., desktop computer, laptop computer, smart phone, tablet, etc.), which may include, or connect to, a webcam and/or microphone. Participants can speak to one another via their webcams and/or microphones, see one another on their displays, and hear one another through their speakers or headphones. In this manner, electronic conferencing simulates face-to-face communication.
Coworkers and other groups often use electronic conferencing to collaborate on projects and/or other endeavors. To this end, some electronic conferencing applications provide virtual whiteboards. Virtual whiteboards display virtual surfaces on which conference participants can draw and make notes. A virtual whiteboard generally occupies a display region on each conference participant's machine, and conference participants can mark on the virtual whiteboard using their pointers, keyboards, and/or other input devices. A virtual whiteboard is normally shared across machines of all conference participants, so that any participant can mark on the virtual whiteboard and see marks that other participants have made.